LP2998EVAL National Semiconductor, LP2998EVAL Datasheet - Page 15

• Manufacturer Part Number: LP2998EVAL
• Description: BOARD EVALUATION FOR LP2998
• Manufacturer: National Semiconductor

Specifications of LP2998EVAL

• Channels Per Ic: 1 - Single
• Current - Output: 1.5A
• Voltage - Input: 2.2 ~ 5.5V
• Regulator Type: Positive Fixed
• Operating Temperature: -40°C ~ 125°C
• Board Type: Fully Populated
• Utilized Ic / Part: LP2998
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Voltage - Output: -

QDR APPLICATIONS
Quad data rate (QDR) applications utilize multiple channels
for improved memory performance. However, this increase in
bus lines increases the current levels required for termination.
The recommended approach in terminating multiple channels
is to use a dedicated LP2998 for each channel. This simplifies
layout and reduces the internal power dissipation for each
regulator. Separate V
bank from the corresponding regulator with the chipset refer-
This circuit permits termination in a minimum amount of board
space and component count. Capacitor selection can be var-
ied depending on the number of lines terminated and the
maximum load transient. However, with motherboards and
other applications where V
plane, it is recommended to use multiple bulk capacitors in
In most PC applications, an extensive amount of decoupling
is required because of the long interconnects encountered
with the DDR-SDRAM DIMMs mounted on modules. As a re-
REF
signals can be used for each DIMM
TT
FIGURE 12. Typical SSTL-2 Application Circuit for Motherboards
is distributed across a long
FIGURE 11. Typical SSTL-2 Application Circuit
15
ence provided by a local resistor divider or one of the LP2998
signals. Because V
part to part variations are minor, there should be little differ-
ence between the reference signals of each LP2998.
OUTPUT CAPACITOR SELECTION
For applications utilizing the LP2998 to terminate SSTL-2 I/O
signals the typical application circuit shown in
be implemented.
addition to high frequency decoupling.
example circuit where 2 bulk output capacitors could be situ-
ated at both ends of the V
Large aluminum electrolytic capacitors are typically used for
their low ESR and low cost.
sult, bulk aluminum electrolytic capacitors in the range of
1000uF are typically used.
REF
and V
TT
TT
30026918
30026919
plane for optimal placement.
are expected to track and the
Figure 12
Figure 11
www.national.com
depicts an
can